9 Oriel 6000 Housing & Arc Lamp

9. Oriel 6000 lamp housing

[D18] Manual for Oriel Model 6000 Q series Lamp housing

http://www.newport.com/p/6251NS

Newport 6251NS Xe 14V 5.4A 75W arc lamp

Oriel 6251 Xe 14V 5.4A 75W arc lamp

I bought this along with a compatible Oriel 68806 50-200W Basic arc lamp PSU and two new 75W Xe arc lamps to provide a (low power) deep UV source for general measurement - see above URL and spectrum below. Newport ignored me when I asked what the NS means in their part number; 'Newport Special'?

This is my low cost alternative to a deuterium lamp which from what I have read has a limited shelf life in the order of about 2 to 5 years; 'D2 lamps *do* have a finite shelf life as D2 can diffuse past glass-to-metal seals.', found here: https://www.chromforum.org/search.php?keywords=deuterium+shelf+life

There are many very old D2 lamps particularly of USSR origin for sale on eBay that will not work, and any modern lamp over 5 years old is also unlikely to work.

Amongst other things, when combined with a monochromator I shall use this Xenon arc lamp to verify luminescence of UV to VIS image converters that will later be used to verify UV laser emissions without endangering the Stellarnet (any exposure to UV is harmful, so I limit it).

The PSU VOLTS/AMPS switch toggle was broken off and I replaced it. It came with a Cramer hour timer but when I changed the PSU voltage selector to 230Vac for UK mains, I discovered despite being hard wired into the supply, the timer was only rated for 115Vac so I removed it. I was impressed that after being driven at twice its rated voltage, its 60Hz synchronous motor still worked at 115Vac, albeit 50Hz.

The PCB PSU bottom brown capacitor next to the yellow transformer looks like it's bulging, but I found this was only the outer plastic cover and not the internal aluminium case, so I ignored it:

Above: 6251NS arc lamp spectrum

Below: Cramer hour timer

Above: inside photo

The Cramer is wired to the main switch bottom left and exits right

Left/right: the broken switch is located below the meter top left

The lamps came with numerous safety notices warning the high pressure could result in an explosion if roughly handled. The Oriel 6000 lamp housing manual actually specifies it is for use with the 6251 lamp but when I assembled the lamp I was surprised the design involves a heavy brass slug at the top with no means of support. Furthermore whilst the external cables to the PSU are EHT rated extra flexible silicone, the internal ones are high voltage rigid cables that are difficult to align without putting stress on the lamp. I put it together but couldn't help thinking the design was idiotic, and made a special effort to arrange the lamp wiring exactly as recommended in the Oriel manual for the housing:

Below - I fired it up and took a few measurements. After about 30 minutes I confirmed the presence of DUV down to the 185nm limit of the Stellarnet, then turned the lamp off and left it to cool down.

PSU & lamp working fine: UV down to 185nm: Full spectrum:

Left: A label on another arc lamp warns not to restart the lamp within 30 minutes. I assumed it would also not be a good idea to move it for that time, so I left it a good hour before I moved it back to storage.

Just as I lifted it up to put it on its shelf, there was an ominous rattle from inside. Dismantling it, I found the arc lamp had severed at the bottom, straight through the glass where the internal cathode lead was sealed within it, with the pressurised envelope above it still intact.

As I had feared, the weight of the solid brass anode slug at the top of the lamp had snapped the new $50 eBay lamp in two (they're over $300 new). At least it didn't explode.

I wasn't going to risk the second lamp until I had a better construction, which meant I would have to modify it first.

The housing is convection cooled so I had to avoid obstructing the heat rising off the lamp. I built a scaffold using a strip of fibreglass PCB sheet clamped at the bottom, supporting two carbon fibre tubes each side, with a solid but heat-expandable flexible support for the brass anode at the top.

I also wondered if I could get the broken lamp to work if it was still pressurised. I really needed some kind of electrically conductive TIM (Thermal Interface Material) between the broken halves of its bottom contact still in its glass body. Mercury was a possibility but it's toxic. It occurred to me gallium might be a suitable choice as unlike Hg it readily wets metal and glass, its resistance is 270nΩ/m at 20°C and it melts at 29.76°C (85.57°F, 302.9K) but only boils at 2400°C (2676K). I bought a 10g syringe of it from eBay China for $4 to try out my idea.

https://en.wikipedia.org/wiki/Gallium

March 2018: Success! See photos below, left to right in chronological sequence: hover over (or click on) each photo for its description.

Gallium permeates metals rendering them brittle - we have yet to see how long this novel repair will last.